A proton and C13 nmr investigation of a number of physical and chemical properties of paramagnetic model heme complexes relevant to the biological role of these complexes as prosthetic groups in hemoproteins is proposed. Both proton and C13 shifts will be used to establish a quantitative relationship between methyl contact shifts and aromatic spin density. The effects of peripheral substituents as well as axial limidazole bonding on the heme electronic asymmetry will then be characterized using the spread of the individually assigned methyl contact shifts, and this data compared to similar data on hemoproteins. The influence of solvent interactions with axial cyanide on the magnetic anisotropy will be investigated to establish the utility of esr data and to develop a probe for monitoring hydrogen bonding of amino acids to cyanide in hemoproteins. The changes in pi bonding to axial imidazoles as a function of variable trans ligands will be elucidated. The role of heme pi contacts with aromatic pi donors/acceptors in modulating the affinity for, and lability of axially coordinated substrates will be characterized. The utility of diastereotopic methylene proton splittings as a probe for the extent on metal-ion displacement from the heme plane will be assessed. The detailed analyses of systematic perturbations on the nmr spectra of model complexes are expected to provide a detailed understanding of the hyperfine shifts in hemoproteins in terms of the electronic stucture of the iron and the protein conformation near the heme pocket. The general utility of proton nmr spectra for investigating structure-function relationships in high-spin myoglobins will be explored. The mechanism of "activating" coordinated ligands in ferric heme complexes will be elucidated and the use of these complexes as possible models for peroxidase and catalases will assessed.